Not the same result at all. You now have lost your phone and the cop has to argue that you smashed it yourself out of spite. There may be more witnesses or evidence after smashing a phone. Presumably there are even phone company records showing when and where a device went dead.

I am not a lawyer but it seems to me, 9 times out 10, the cop would prefer a cleaner result - they confiscate your device, and oops, when you get it back, the video is gone.

If cops wanted clean results, they wouldn't do anything that looks bad on your smartphone camera to begin with.

Why wouldn't they just confiscate it, and "oops, it fell in a bucket of water"?